fs.md

Node Filesystem

A local pet shop keeps a database for all the pets they have in stock. However, they need you to build a command-line application in Node to handle a variety of subcommands and log the results to the console.

The subcommands will be in the form of create, read, update, and destroy (CRUD). These subcommands will manage their database, which is a JSON-formatted pets.json file. Once the subcommand is correctly handled, the app will need to log an appropriate result to the console. Details of the subcommands the app will need to handle and their output can be found below.

Getting started

After you fork and clone this repository to your development environment, change into the project directory and install any dependencies.

cd path/to/project
npm install

Ignore node_modules from the repository. This prevents your node modules folder from being included in your repository.

echo 'node_modules' >> .gitignore

Create a pets.js file for your filesystem code.

touch pets.js

Assignment

Your first task is to build a command-line application that displays its usage, ideally to the standard error channel, when invoked without a subcommand. The app should exit the process with a non-zero exit code to indicate that it failed to complete any work.

$ node pets.js
Usage: node pets.js [read | create | update | destroy]

Your next task is to refactor the application to handle the read subcommand via the process arguments, read the pets.json file, parse its data to a native JavaScript object, and log it to the console. If the call to the filesystem fails for any reason, it should throw the resulting error.

$ node pets.js read
[ { age: 7, kind: 'rainbow', name: 'fido' },
  { age: 5, kind: 'snake', name: 'Buttons' } ]

Additionally, your application must handle the read subcommand when given an index. In this case, it must read the pets.json file, parse its data to a native JavaScript object, access the correct record, and log it to the console. If the call to the filesystem fails for any reason, it should throw the resulting error.

$ node pets.js read 0
{ age: 7, kind: 'rainbow', name: 'fido' }

$ node pets.js read 1
{ age: 5, kind: 'snake', name: 'Buttons' }

Additionally, your application must handle the read subcommand when given an out-of-bound index. In this case, it must display a more specific usage to the standard error channel and exit with a non-zero exit code.

$ node pets.js read 2
Usage: node pets.js read INDEX

$ node pets.js read -1
Usage: node pets.js read INDEX

Finally, your application must also handle the create subcommand. Only when given an age, kind, and name will it create a record in the database. Remember to convert the age into an integer. For example:

$ node pets.js create
Usage: node pets.js create AGE KIND NAME

$ node pets.js create 3
Usage: node pets.js create AGE KIND NAME

$ node pets.js create 3 parakeet
Usage: node pets.js create AGE KIND NAME

$ node pets.js create 3 parakeet Cornflake
{ age: 3, kind: 'parakeet', name: 'Cornflake' }

$ node pets.js read 2
{ age: 3, kind: 'parakeet', name: 'Cornflake' }

If the pets.json file ever becomes corrupted, you can reset it with the git checkout command.

$ git checkout -- pets.json

Bonus

Refactor your app to also update records in the database when given the update subcommand. Remember to convert the age into an integer. For example:

$ node pets.js update
Usage: node pets.js update INDEX AGE KIND NAME

$ node pets.js update 1
Usage: node pets.js update INDEX AGE KIND NAME

$ node pets.js update 1 9
Usage: node pets.js update INDEX AGE KIND NAME

$ node pets.js update 1 9 cat
Usage: node pets.js update INDEX AGE KIND NAME

$ node pets.js update 1 9 cat Rosey
{ age: 9, kind: 'cat', name: 'Rosey' }

$ node pets.js read 1
{ age: 9, kind: 'cat', name: 'Rosey' }

Bonus

Refactor your app to also destroy records in the database when given the destroy subcommand. For example:

$ node pets.js destroy
Usage: node pets.js destroy INDEX

$ node pets.js destroy 1
{ age: 5, kind: 'snake', name: 'Buttons' }

$ node pets.js read
[ { age: 7, kind: 'rainbow', name: 'fido' } ]

Bonus

Add a shebang(#!) to the start of the pets.js file and modify its permissions so it can be run from the command-line without the node command. For example:

$ ./pets.js read
[ { age: 7, kind: 'rainbow', name: 'fido' },
  { age: 5, kind: 'snake', name: 'Buttons' } ]

$ ./pets.js read 0
{ age: 7, kind: 'rainbow', name: 'fido' }

$ ./pets.js create 3 parakeet Cornflake
{ age: 3, kind: 'parakeet', name: 'Cornflake' }

$ ./pets.js read
[ { age: 7, kind: 'rainbow', name: 'fido' },
  { age: 5, kind: 'snake', name: 'Buttons' },
  { age: 3, kind: 'parakeet', name: 'Cornflake' } ]